Method of roller coating



2 Sheets-Sheet 1 May 9, 1944. J. s. THOMPSON METHOD OF ROLLER COATINGFiled Aug. 5, 1940 May 9,1944. J. s. THoMPsoN METHOD oF ROLLER coATINGFiled Aug. 3, 1940 2 Sheets-SheKet 2 Patented May 9, `1 944 2,848,698METHOD oF ROLLER coA'rING John S. Thompson, Detroit, Mich., assignor toParker Rust Proof Company, Detroit, Mich.

Application August 3, 1940, serial No. 351,900

7 Claims.

This invention relates to the coating of metal and particularly toprepare the surface of metal to receive paint, dye, lacquer or the like,and is a continuation in part of my application, Method of rollercoating, Serial No. 199,129, filed March 31, 1938. It has been known forsome time that the surface of metal may be changed or converted from oneof metal to one of non-metal by the use of various solutions. The artfirst taught the submerging of the article to be coated or convertedinto the solution and allowing the article to remain therein until thecoating operation had been completed. Later it was discovered thatcoating could be obtained by spraying the solution upon the article tobe coated either while the article remained stationary or while it wasbeing passed through a chamber upon a conveyor, the spray bombarding thearticle with solution and bringing about the conversion necessary tocompletely coat the article. It has now been discovered that finecorrosion retarding coatings may be obtained upon metal surfaces bypassing the metal through a plurality of rollers which have Ibecome wetwith a solution which will convert the surface from one of metal to oneof nonmetal.

In the preparing of metal surfaces to resist corrosion a great manysolutions are known which in turn form many types of coatings, according.to the solution used. Of the better known coatings the phosphates,chromates, oxalates, and oxides lead the field today.

The method herein disclosed is particularly useful at the mill or pointof metal manufacture because it enables the manufacturer to coat thesheets as they come from the nal manufacturing step preparatory toshipping. The problem has presented itself of preventing corrosion ofsheets between the time they leave the mill and the time they reach thepoint where they are to be used. At times the sheets are not used forweeks and even months and in this interval ,corrosion sets in andnecessitates an additional operation to remove this rust, beforepainting. With the present method the sheets are treated immediatelyfollowing the last manufacturing step so that the method lits into themodern mill or modern manufacturing plant as another `step or operationand saves the user forwarding his stock to a jobber or separate plant tohave his sheets prepared for painting. l n

The principal object of the present invention is to provide a new andimproved method for converting the surface of metal from one of metal toone of non-metal.

Another object of the present invention is to provide a new and improvedmethod of coating metal which aids in the precleaning of the sheets, therollers per-forming a scrubbing and pressure action thereon whichlessens the effect of extraneous and deleterious lmatter that usuallyadheres to the sheets in their travel through the various manufacturingsteps.

A still further object is to provide a new and improved method forcoating metal whereby thc surface of the metal is not only transformedfrom one of metal to one of non-metal, but the sheets are dried, Waterrinsed and acid rinsed to prepare them for the immediate application ofpaint, lacquer, dye or the like.

The above and other objects will appear more fully from the lfollowingmore detailed description, and from the drawings, wherein Fig. 1 is atop plan view of the apparatus used to carry out this method of coatingmetal; and

Fig. 2 is a section of the apparatus taken substantially on the line 2-2of Fig. 1.

Referring now to the drawings, the numeral I9 designates supportingmeans for supporting the superimposed apparatus for carrying out themethod herein disclosed. Conveniently located at one end of theapparatus is a solution reservoir Il above which is suitably located anadditional solution reservoir I2 for a purpose later to be described.Conveniently located at the other end of the apparatus is a pair ofrinsing tanks I3, I4, and midway between the solution tanks and rinsingtanks there is provided a heating and drying chamber comprising a heatproducing means, which in the drawings is shown as a gas pipe I5 havinga plurality of holes I6 therein for the gas flame which in turn impingesa base plate having a plurality of flns I1 formed integral with the baseof the heating chamber merely as an illustrative example.

and running transversely thereof to provide a greater heating area tosaid chamber. Any well known heating means, such as coal or electricitymay be used, gas being used in this illustration Immediately above andformed integral with the heating means Just described is a heatcirculating chamber into which air is brought from atmosphere throughduct I9, said duct being provided with damper means 28 to close the ductwhen required. A circulating fan 2| is conveniently provided within theheat circulating chamber I8, the same being rotated by means of motor22. superimposed upon and built integral with the heat circulatingchamber I8 is a drying chamber 23. A warm air duct 24 connects heatcirculating chamber |8 and drying chamber 23 and a plurality ofdirectional bales 25 act to direct the warm air in the circuitous pathdesired. An additional duct 26 is provided to connect the drying chamber23 with the heat circulating chamber I 8 and to return part of the airback into the heat circulating chamber and deposit the same directlyback to the circulating fan 2| so that it may -be again passed over theheated fins I1 and returned to the drying chamber 23. A damper 21 isconveniently located within duct 26 so that this duct may be closed whendesired. -A hood 28 is located directly above and built integral withthe drying chamber 23 and provides means for taking oil' the fumes bymeans oi' a stack 29 having a damper 38 located therein to close thestack when desired. Suspended within the drying chamber 23 is a pair oi'endless conveyor` chains 3| with a plurality of spaced transverse ribs32 supported thereon (shown -best in Fig. 1 of the drawings) said ribshaving secured thereto a plurality of pointed pins 33 which act assupports for the metal sheets as they are carried by the conveyor. Thepins are tapered or pointed to reduce the area covered on the sheet bythe pin so that practically the entire sheet will receive warmed airduring the drying operation. The conveyor chains 3| are trained about apair of sprocket wheels 34, and to prevent the conveyor chains fromsagging there are provided supports 35 comprising a pair of angle ironswhich in turn support each chain as they make their run. The numeral 36designates a transverse opening or slot provided to allow the sheets topass into the drying chamber 23 and numeral 31 designates an opening ortransverse slot to allow the sheets to pass from the drying chamber 23to the rinsing operation.

Suitably located within the solution reservoirs is the mechanism forapplying the corrosion retarding solutions which comprises a solutionfeeding roller 38 which is at all times partially submerged in thesolution, contained in reservoir I2. Roller 38 is at all times in meshwith a driving roller 39 which in turn is in mesh with a driven solutionfeeding and spreading roller 48. Driven roller 4| is at all timespartially submerged in solution reservoir II and is at all times in meshwith driven solution spreading and feeding roller 42. To compensate forthe various thicknesses of sheets which are passed between rollers 48and 42 there is provided vertical adjusting means located adjacent lowerreservoir I I, the adjusting means comprising a slidable bearing 43 foradjusting roller 42 and a slidable bearing 44 for adjusting roller 4| bymeans of adjusting screws 45, 46. Roller 48 is mounted on shaft 48, theshaft being mounted in arm 49, which is integral with -arm 58 which isrotatably mounted on shaft '"41. The numeral 5I designates a portion ofthe machine frame in which shaft 41 is mounted. Portion 52 of themachine has a slot 53 formed therein to allow for movement of bolt 54 sothat the same may be either raised or lowered in said slot, saidadjustment permitting roller 48 to be moved toward or away from roller42. These rollers are operated through a train of gears 55, 56, 51 whichare suitably mounted on the end of shafts 41, 48, 58. 'I'he lowerfeeding rolls 42 and 4| also are operated through gears 59 and 88,

v gear 59 being directly beneath gear 51 and in mesh with same. 'Themachine frame projection 52 has mounted thereon a scraper 6| which isprovided with an adjusting means 62. Lower coating roller 42 is alsoprovided with an adjustable scraper 63 provided with adjusting means 64.The main driving means comprises pulley 65 having a belt 66 trainedthereon, said pulley being secured to shaft 41 so that when the shaft isrotated gear 56 is rotated and in turn rotates gears 55, 51, 59 and 68.A pair of guide rollers 61, 68 are provided to guide the sheets so thatthey will pass between the coating rollers 48, 42. Steam pipes 69 and 18are provided in the upper and lower solution reservoirs to keep thesolution at the temperature desired for processing. A drain pipe 1| isprovided in reservoir to clean out the same when necessary.

After the sheets have passed through the drying chamber 23 a pluralityof apposed guide rollers 12, 13, 14, 15 carry'the sheets between rinsingmeans comprising a pair of transverse pipes 19, 11 containing aplurality of apertures therein to allow the rinsing medium to escapeonto the sheets. 'I'hese pipes are fed by stand pipe 18 and directionalbales 18, 80, direct the spray so that it impinges directly upon thesheets and thoroughly sprays the entire area. beneath the pipes. Anotherpair of rollers 8|, 82 drive the sheets between an additional rinsingmeans comprislng a, pair of transverse pipes 83, 84, containing aplurality of apertures therein to allow the rinsing medium to escapeonto the sheets. These pipes are fed by stand pipe and directionalbailies 86, 81, direct the spray so that it impinges directly upon thesheets and thoroughly sprays the entire area. beneath the pipes. Anadditional pair of driving rollers 88, 89, carry the sheets from beneathspray pipes 83, 84, and out of the apparatus. Driving rollers 12, 15, 8|and 88 are driven by belts 98, 9|, 92, 93 trained about pulleys 84, 95,96, 91 (see Fig. 1 of drawings). 'I'he rollers as shown are of rubberand bonded to shafts as follows: roller 12 to shaft 98, roller 13 toshaft 99, roller 15 to shaft I 88, roller 14 to shaft |8I roller al toshaft luz, roller sz to shaft los, roue; 88 to shaft |84, and roller 89to shaft |85. Although rubber is shown, any adsorbent material may beused, or metal rollers smooth or suitably corrugated may be substituted.Steam coil |86 is conveniently located in reservoir I3 to keep therinsing solution at the desired temperature and steam coil |81 islocated in reservoir I4 to keep the rinsing solution in this reservoirat the desired temperature. A drain pipe |88 is located in the bottom ofreservoir I3 so that the same may be dumped when necessary.

Although the process may be operated with many different corrosionresistant solutions to coat many types of metals, such as iron, steel,zinc, cadmium, copper and lead, there are given below a few specificexamples of corrosion retarding solutions. These examples are given byway of illustration and not limitation, it being understood that widedeviations are possible in ingredients, proportions. temperatures, etc.,without departing from the spirit of the invention:

To coat zinc use- Parts by volume 1. '75% phosphoric acid 8 60% nitricacid 6 Water To coat zinc, iron and cadmium use- 2. Zinc dihydrogenphosphate lbs-- 8.2

50% zinc nitrate solution lbs-- 36.5 '70% nitric acid av.ozs 14 Coppercarbonate grams-- 57 Wetting agent (Novonacco NN) ..cc 'Z5 Water lbs--74 To coat iron and steel use- Per cent 3. Zinc dihydrogen phosphate 2.875% phosphoric acid 2.5 Chromic acid 1.0 Wetting'agent (Novonacco NN) .4Balance Wate To coat iron and stee1 use- 4. Zinc dihydrogen phosphategrams 140 Copper nitrate do 28 Water liters.k 4

To coat iron and steel use- Per cent 5. 100% phosphoric acid 8.5 Chromicacid 9.0 Wetting agent (Duponol) 1.0 Balance Water To coat zinc use- 6.Oxalic acid grams-- 360 Sodium nitrate do 120 Ferrous sulfate -do 60Fullers earth 1bs 4 Water gallon 1 To coat iron, zinc, cadmium, copperand lead use- 7. Oxalic acid lbs-- A rinse with a solution containingchromic acid or other hexavalent chromium compounds, preferably in anacid medium may be used following the use of any of the above coatingsolutions to enhance the corrosion-resistance and paint-bondingproperties of the coatings.

In some instances it is diilicult to obtain uniform wetting of the metalby the coating solution especially where relatively high concentrationsof chromic acids or other hexavalent chromium containing solutions areemployed. In such instances it may be necessary to rst pre-treat themetal by means of solutions which will produce a surface which is morereactive with the hexavalent chromium containing solution than theuntreated metal.

The first treatment, as indicated above, may result in a coatingessentially oxide, a coating of a metallic deposit, a coating of a saltof iron and additional salts, if desired, or in mixtures of any two orall three of the types mentioned, and may include sulphides or otheringredients which perform like functions.

For example, the first step may be treatment with any one of the manyknown phosphate coating solutions, or with solutions of organic coatingacids, such as described in Patent No. 1,911,537, to Robert R. Tanner,for example. But, if a solution of this type is employed. whether withor without oxidizing agents, accelerating metal compounds, or otherobvious modifications, the treatment should be limited so as to producea much thinner coat than has been hitherto generally desired as aproduct of such solutions, so that the major part of the nal coating isproduced by the second treatment, and preferably so that the secondsolution may treat the metal surface as well as the product of the iirsttreatment.

The following examples will serve to illustrate means by which oxidecoats may be produced upon metal.

Upon steel, rst coatings have been produced by treating the surface ofthe metal with a solution for two minutes where the solution containedas its active chemical 2.5% of the nitrates of manganese, chromium,magnesium, cobalt, iron. lead, cadmium, zinc, aluminum, mercury, orcopper, or 5% nitrate of strontium, barium, or calcium.

Widely different concentrations of solutions may be employed andlikewise the temperature and time of treatment may be varied, suchvariations in the strength of the solution, and the time and temperatureof treatment being adjusted to obtain the desired thickness of coatingin accordance with the principles stated in con-` nection with thedetailed disclosure of the second treatment.

As a specific example a solution of the following analysis may beapplied to steel sheets by rollers and be allowed to stand in contactwith the metal for a period o! thirty seconds.

The metal which during this time receives a coating which ispredominantly oxide, after receiving a water rinse, is roller coatedwith a solution having the analysis of Per cent Phosphoric acid 6Chromic acid 3 Trivalent chromium .5

The coated sheet is then heated at a temperature of 550 F. for 10minutes in order to render the applied film insoluble.

The general procedure involving the application of solutions adapted tocoat the metals by means of rolls is carried out as follows:

The solution to be used to convert the surface of the metal to betreated from one of metal to one of non-metal is rst placed in thesolution reservoirs Il and I2 and the solution` for rinsing is placed inthe rinsing solution containing tanks I3 and I4. If desired, steam isthen injected into the various steam coils in the reservoirs sothat thecorrosion retarding and rinsing solutions will become heated to thedesired temperature. The means for heating the heating chamber beneaththe fins I1 is then ignited and fan 2| is turned on. The damper 20 induct I9 remains at its dotted line open position, as shown best in Fig.2 of the drawings, so that air is brought in from atmosphere and heated.Inasmuch as it is necessary to have the proper pressure on the Work |09as it passes between rollers 40 and 42, and also to compensate for thevarious thicknesses of material being run through said rollers, the geartrain controlling these rollers must be adjusted so that the properopening remains constant all during the run. To adjust solutionspreading roller 48, bolt 54 located in slot 53 in frame portion 52 ismoved upwardly, and, inasmuch as rollers 48, 39 and 3B are journaled inmovable arm 58, which in turn is rotatably mounted on shaft 41, gears55, `56 and 51 located on the ends of shafts 41, 48 and 58 respectively,remain in mesh and the peripheral rubber surface of rollers 48, 39 and38 also remain in frictional engagement ready for use. To compensate forthis upward movement of rollers 48, 39 and 38, rollers 42 and 4| must bemoved upwardly so that the gearing on their shafts is also in mesh andthe gear 59 remains in mesh with gear 51. Adjusting screw 45 allows formovement upwardly or downwardly of roller 42 and adjusting screw 46allows for movement upwardly or downw :ily of roller 4|, so that theirgears 59 and 68 are always in mesh and the face of these two rollers arealways in frictional contact. The scraper 6| mounted on machine frameprojection 52 is then adjusted by means of adjusting screw 62 so thatthe proper pressure is brought to bear on roller 39, said scraperpreventing any sludge from contacting solution spreading roller 48, andalso to provide a means to control even distribution of the corrosionretarding solution when transferred to roller 48. 'I'he lower coatingroller scraper 63 is also similarly adjusted by means of adjusting screw64 for a like purpose. The solution spreading gear train is now set inmotion beit 66 turning on pulley 65 in a counter-clockwise directionwhich in turn drives driving roller 39 in a counter-clockwise directionas shown by the arrow in Fig. 2 of the drawings. As rollers 40 and 38are in mesh with driving roller 39 roller 38 will turn in a clockwisedirection and roller 48 in a clockwise direction, as shown by the arrowin Fig. 2 of the drawings. Roller 38 being partially submerged incoating solution in reservoir I2 picks up solution, and inasmuch asrollers 39 and 48 are in frictiona-l contact at all times this solutionis transferred to solution spreading roller 48 which in turn transfersthe solution to the work |89. Likewise roller 4| is also partiallysubmerged in coating solution in reservoir and inasmuch as roller 4| isin mesh with solution spreading roller 42 at all times, solution istransferred to roller 42 and thence to the work |89, the rollers turningin the direction of the arrows shown in Fig. 2 of the drawings. The work|89 passes first through guide rollers 61, 68 and when the work ispassed between solution spreading rollers the pressure exerted upon thework by the rollers tends to squeeze the solution between the rollersand the surfaces of the Work, thereby causing wetting of said surfaces,and consequently the surface of the work is quickly transformed from oneof metal to one of non-metal. Upon the completion of the conversionstep, i. e., converting the surface from one of metal to one ofnonmetal, by means of the spreading rollers 48, 42, impregnated withcorrosion retarding solution, the work passes through opening 36 intodrying chamber 23, where it is picked up by conveyor 3| and transportedthrough this heating chamber at a predetermined speed to allow for athorough drying of the work. In some cases, depending upon the type ofsolution being used, and the character of the work being'processed, heatmay be required to produce the coating, the rollers merely serving as ameans of application. Also,

in some cases, after applying the solution, by means of the rollers,time is required to complete the conversion of the surface of the metalfrom one of metal to one of non-metal, heat not being necessary.

'I'he conveyor chains 3| which in turn support the transverse crossmembers 32 having the supporting pins 33 thereon is driven by a sourceof power not shown, at a convenient speed to thoroughly dry the workbefore it reaches the rinsing operation. There is an opening betweeneach cross member to allow heated air to pass therebetween, and inasmuchas the work is supported by the pointed pins 33 the heated air isallowed to contact the under surface o1.' the work and dry the same.Warm air also passes around the ends of the conveyor and between thesheets, as shown best by the arrows in Fig. 2 of the drawings and thusthe air above the top of the work becomes warmed and infturn tends todry the top of the sheets as they pass along on the conveyor. If it isdesired to increase the temperature of the air within the hood 28, thedamper 38 in stack 29 is closed and the warm air will follow acircuitous path back down through duct 26 and will again be blown by fan2| over the heating means in the base of warm air chamber |8 and upthrough duct 24 and directional baffles 5 to again be used as a dryingagent for the ork. Damper 28 in duct I9 may also be closed so that nofresh air will enter the warm air chamber 8 and this in turn will raisethe temperature of the air already in drying chamber 23, and convertdrying chamber 23 into a baking oven of any desired temperature.

When the work |89 has been dried it passes from the conveyor throughopening 31 and between driving and guide rollers 12, 13, 14, 15, rollers12 and 15 being driven by means of belts 98, 9| trained about pulleys94, 95 (see Fig. 1 of the drawings). Rollers 13, 14 are rotated byfriction contact with the work. As the work leaves rollers 15, 14, it ispassed between rinsing pipes 16, 11, which run transversely of the workso that the sprays from the apertures therein thoroughly rinse theentire surface of the work passing beneath the pipes, the directionalbailies 19, 88 guide the rinsing solution directly on the work. Therinsing solution, usually water at this step of the process, is heatedin reservoir I3 by means of steam coil |86 and is pumped to riser pipe18 by a pumping means, not shown, from whereI it enters pipes 16, 11.'After rinsing, the solution runs off the work and falls into reservoir|3 to be repumped to riser 18 and used over and over again. 'Ihe workthen passes between drivrg roller 8| and driven roller 82, drivingroller 96, driven roller 82 being rotated by frictional contact with thework as it moves between the rollers. The work is then passed between apair of additional rinsing pipes located directly above reservoir I4,the pipes being located above and below the work and run entirely acrossthe work. A number of apertures allows the solution to be sprayed ontothe work and directional bafes 86, 81 guide the ow of solution directlyagainst the work. The rinsing solution is heated in reservoir |4 bymeans of steam coil |81, and is pumped, by means not shown, to riserpipe 85 from where it is carried to pipes 83, 84 and onto the work, theexcess solution returning to reservoir I4. This final rinsing solutionusually contains a dilute solution of chromic acid, phosphoric acid,oxalic acid or a salt of iron, chromium or being driven by belt 92trained about puuev aluminum, such as aluminum nitrate or sulphate,ferrous sulphate, ferric nitrate and chromic sulphate or nitrate. It hasbeen found that by the use of a final rinse, such as that describedabove. paint blistering is reduced to a minimum. The solution may beused from 150 to 180 F. From i to 21 ounces of the acid or salt per 100gallons of water is the preferred strength from the standpoint ofeconomy, although stronger solutions are just as effective. A treatmentof one minute in these solutions is sufcient. Following the abovedescribed rinse, the work passes between driving roller 88 and drivenroller 89, driving roller 88 being driven by means of belt 93 trainedabout pulley 91, roller 89 being driven by frictional contact with thework. Having passed through the last two mentioned rollers the work isready to be force dried or air blown, following which paint may beapplied.

As an example of a solution for coating zinc, iron and cadmium to befllowed with a chromic acid rinse, the following is given:

To 'I4 pounds of water add- Zinc dihydrogen phosphate lbs 8.2 50% zincnitrate solution lbs 36.5 '70% nitric acid av. ozs-- 14 Copper carbonategrams-- 57 .Wetting agent (Novonacco NN) cc 75 (Novonacco is atrade-marked product, obtained by the interaction of a hydrocarbon withsulphuric acid, the product is manufactured by The National Aniline andChemical Company, Inc., of New York, N. Y.) A coating produced with theabove solution may be followed by a rinse comprising 14 ozs. of chromicacid per 100 gals. of water used.

It will be seen from the above description that there is here set fortha new and unique method of coating metal preparatory to-painting. Thismethod may be installed at the mill and become another step in themanufacture of sheets or it may be installed in the jobbing plant wherethe sheets may be treated before painting and formed into the finishedarticle. Also one side only of the sheet need be coated, the reservoirholding the coating solution supplying either the upper or lower coatingroller may be emptied so that only one roller receives solution. Wherecommon immersion or spray methods of applying chemically reactivecorrosion retarding solutions are employed and the solution is appliedover and over again, it must be replenished with proper chemicals tokeep it in balance so that it will coat successfully. The roller methodherein disclosed requires replenishing ofthe solution reservoirs insofaras the solution being used is concerned,

but where the applying rollers transfer the solution from the solutionreservoirs to the work and the solution stays on the work and is notreturned to the solution reservoirs, the problem of keeping the solutionin balance is overcome.

What I claim is:

1. In the chemical treatment of a metallic surface to form acorrosion-resistant paint-holding base thereon, the steps of moving ametallic surface in non-immersed condition past a roll having a yieldingsurface thereon, pressing the roll against the metallic surface duringsaid moving, feeding an aqueous solution containing paintbase-fonningchemicals between said roll surface and saidmetallic surface, adjustingthe pressure of the roller against the metallic surface so that saidsolution is pressed into chemically reactive contact with said metallicsurface and the desired amount of solution remains on said metallicsurface and forming a paint-holding coating on the metallic surface fromthe chemicals so applied and their reaction products.

2. A method in accordance with claim 1 and comprising rst applying a nlmof the solution to a roller and then transferring the solution from theroller to said surface.

3. A method in .accordance with claim 1 wherein the treated metallicsurface is of the class consisting of iron, zinc and their alloys.

4. A method in accordance with claim 1 wherein the treating solution isan aqueous solution of compounds of P04 and of compounds of hexavalentchromium. Y

5. A method in accordance with claim 1 wherein the treated metallicsurface is of the class consisting of iron, zinc and their alloys andthe treating solution is an aqueous solution containing compounds ofP04.

6. A method in accordance with claim l wherein the treated metallicsurface is of the class consisting of iron, zinc and their alloys andthe treating solution is an aqueous solution containing compounds ofP04, and comprising the added step of applying a solution containinghexavalent chromium to coating produced by said chemicals.

'1. In themethod of providing a metallic surface with a corrosionretarding and paint-bonding coating, the steps of moving said surface ina non-immersed condition past a roll, feeding to said surface in aposition to be spread on the surface by said roll a solution adapted toprodtclng a more chemically reactive surface than is the metallicsurface with a solution containing hexavalent'chromium, and thereafterapplying in the same manner a solution containing hexavalent chromium.

JOHN S. THOMPSON.

